1. Field of the Invention
This disclosure relates to the field of cardiovascular exercise machines. In particular, to a conveyor chain for treadmills which are designed to provide a moving staircase. These are often referred to as stepmills.
2. Description of the Related Art
The benefits of regular aerobic exercise on individuals of any age are well documented in fitness science. Aerobic exercise can dramatically improve cardiac stamina and function, as well as lead to weight loss, increased metabolism, and other benefits. At the same time, aerobic exercise has often been linked to damaging effects, particularly to joints or similar structures, where the impact from many aerobic exercise activities can cause injury. Therefore, those involved in the exercise industry are continuously seeking ways to provide users with exercises that have all the benefits of aerobic exercise, without the damaging side effects.
One relatively low impact exercise is walking. Walking has a number of advantages over its faster relative, running. In particular, walking causes much less stress on body structures in the legs, feet, and hips. In a walking motion, the human body generally never completely leaves the ground while, in a running motion, the body is suspending midair for a short period of time with each stride. Thus, while walking, knees and other structures absorb an impact from the foot's contact with a surface, but the entire weight of the individual is generally not absorbed by the body as it is in running. For this reason, walking is generally an acceptable exercise for a large number of people and even for the elderly and those with joint or other issues. Further, the impact of walking can be further reduced by walking on a treadmill or other exercise device as opposed to walking outside. The tread of a treadmill can be purposefully engineered to absorb and reduce impact from footfalls, making the walking motion produce even less impact on the body.
Walking as an exercise, however, has a number of built-in limitations and these can be exaggerated when one is intending to walk on a machine in the home or gym such as a treadmill. Many of the problems relate to walking's built in limitations for strenuousness. The average human will generally naturally walk around 3 to 3.5 miles per hour and most humans cannot walk above 4 to 5 miles per hour without specific training. Generally, at higher speeds, the person has to switch to a running motion in order to maintain the desired speed. It is often accepted that speeds between 4 and 6 miles per hour require the average human to jog, while speeds above 6 miles per hour require a running motion. Humans can obtain very fast speeds while running with an average person being able to sprint at over 10 miles per hour. Further, some studies have indicated that any person's natural walking speed may be preferentially selected to minimize work for desired distance and time. Thus, natural walking as an exercise can be problematic because humans may naturally walk in a very efficient fashion, which can minimize its exercise potential.
While a sustained walking speed of 4 mph can prove plenty strenuous for many people, for those looking for weight loss and strong cardiovascular workouts, walking, even at their top sustainable speed, can require a very long workout to be equivalent to a relatively short run and the time for such a workout may not be available. The time required by walking can be particularly problematic for home exercise machines where the average user can find walking in-place for a long period of time boring since there is no changing scenery or people to talk to.
For those who are interested in using an exercise machine for strenuous walking, the common way to increase the strenuousness of the activity is to increase the incline of the tread forcing them to consistently walk “uphill” or engage in more of a hiking or climbing exercise. Walking at even a relatively slight angle above neutral (or level) has been shown to dramatically increase the strenuousness of the walking. However, traditional treadmills often have problems producing higher inclines. Specifically, traditional treadmills could generally only obtain a maximum incline of around 10-15 percent.
To go to higher inclines, many workout machines will transition from the standard smooth running belt of a treadmill to a conveyor chain that is designed to simulate steps. These are often referred to as “stepmills”. The act of going up stairs has been long known to be a vigorous exercise because it not only requires moving the body (where moving the body mass provides the resistance) horizontally, but vertically in a near equal amount. Further, walking up a staircase as an exercise generally causes the person doing it to work multiple of their large lower body muscles. This is an effective way to burn calories, build muscle mass, and sculpt one's appearance. Further, stair climbing also assists in working on balance since the person's mass is generally being lifted by a single leg at a time and provides an intense cardio workout due to its difficulty.
Originally, those interested in performing stair workouts would simply utilize a convenient flight of stairs. Probably the most memorable stair workout occurs in the movie “Rocky” with Rocky Balboa running up the 72 stone steps in front of the Philadelphia Museum of Art to evocative music and raising his hands in triumph at the end. That scene, which is considered by many as one of the greatest scenes in movie making, may have even served as the inspiration for a resurgence in stair climbing as an exercise. Even today, stair-climbing races are popular fundraisers in a number of cities and many fitness trackers will separately track stair climbing.
While running or walking up an actual staircase can be a highly effective workout, it does present a reasonably high danger of falling, can be of limited interest and availability due to a limited number of stair steps available in a home or even gym setting, and can be difficult in inclement weather if the staircase is outside. For that reason, the concept of stepmills seek to provide what is essentially an endless staircase indoors to allow for a similar exercise to be performed in limited space and over a longer period of time.
Originally, stepmills operated along the same basic principle as the escalator moving stairway which is a venerable design generally considered in its modern form to date back over 100 years and in older forms almost 200 as evidenced by documents such as U.S. Pat. Nos. 25,076; 406,314; and 479,864. People just simply use the structure of escalators in reverse by attempting to walk up a staircase that is actually moving down. The stair operation of many stepmills has also been traditionally similar where the stairs each comprise a solid component “block” mounted on a chain. Each of the blocks is generally triangular in cross-section and includes a generally 90-degree corner on the user facing side with one of the faces on the opposing side. A chain is then used to interconnect and mount the faces together. In this way, when the chain is arranged at an angle, the blocks form a series of steps. A user is supported on the chain by simply supporting the blocks on a truss system and platform that serves to hold the user's body weight.
While this structure is highly effective for an escalator to move people between floors of a building, it actually has some major problems in conjunction with an exercise device. The most notable of which is its vertical size. Because the stair chain needs to be an endless loop, the height of a stepmill chain is generally substantial. In particular, the base is commonly quite high off the ground as the chain and blocks need to clear the floor a sufficient distance to allow the full size of each block to not impact the floor as it goes around under the device and under the chain part being used. Further, the top portion of the device is generally defined by the number of steps the device has. As a step is commonly between 8 and 12 inches, to have even a small number of steps be available to the user (for example 4), the top of the top block will commonly be more than 4 feet off the ground. To deal with this some manufacturers broke the step into two components, a tread and a kickplate, which could rotate about each other but were individually quite thin. While this allowed the components to generally arrange themselves in a more co-planar arrangement when returning under the step arrangement, the original height still had to be sufficient to allow the kickplate and tread to turn the bottom corner closest to the floor. Thus, while the initial height did not have to be double the stair rise, it was often still at least a single rise and often more.
A second problem created by these kind of stepmills is the difficulty in getting on and off them. In an escalator, the landing platform at the bottom is actually suspended above the working elements of the escalator and the escalator belt actually extends under the floor. This allows the belt to have a different angle at the discharge end that causes the blocks to slide together so their upper surfaces form a generally co-planar flat surface across multiple stairs. This allows a user to step on or off without having to step up or down. In a stepmill machine, however, this is generally not possible as the machine cannot be built into the floor, but needs to rest on the floor.
Thus, getting on the machine commonly requires a user to step up the distance of at least one, and often more, stairs to get on the machine. This can be uncomfortable. Further, it can create a fairly major safety situation as if a user was to inadvertently go too far back on the machine and the stair tilted out from under them as it went around the lower corner and began its turn to return to the top, the user has a rather substantial distance to fall off the lowest step which can lead to major injury.
Because of these and other similar problems, the stepmill fell out of favor for gyms and home exercise. Instead, it was replaced by a “stepper” or a machine that utilized pneumatic or hydraulic resisted levers to simulate stair movement in the legs. In these systems, the user would lift their foot on a lever that would then be pushed up by a piston at generally the same rate they moved against the base of their foot. Upon, reaching the top of the “step”, the user would then push the lever down against the piston to provide the exercise stroke, while simultaneously raising their other foot. In this way, a “high step” kind of motion similar to that of stair stepping was created. While this was an effective exercise, it was not actually stair climbing as the user did not actually lift their full mass with each step. Instead, the majority of resistance was actually provided by contracting the piston which their mass assisted with.
Stepper machines have also fallen out of favor due to them not being particularly comfortable to use since the motion is somewhat unnatural and have been replaced more by elliptical machines or standing bikes that utilize a rotational motion instead of the multiple levers reducing impact on the body but provide a similar “high step” type motion. The stepmill, however, has begun to see a comeback with one of its modern counterparts having become quite common. That is the endless ladder. The endless ladder is not climbing on stairs where the foot is placed on a flat horizontal surface, but by climbing on cylindrical rungs. As the rungs can be much smaller than the stair tread and can be circular in diameter, the step of a rung is much smaller than a traditional step. This allows the base of the machine to be much closer to the ground. However, the motion of an endless ladder can be a bit uncomfortable and unnatural as one is commonly climbing at an angle and the user's full foot does not contact the rung. Further, because an endless ladder requires a user to use their hands on a “higher” rung to stabilize themselves, the tread of these devices are often very long meaning that while they may not have as much vertical height to horizontal height as a stepmill, they often require even more space to handle their large tread and rotating the base through multiple angles.